(i) Technical Field
The present invention relates to focal-plane shutters and optical devices.
(ii) Related Art
There is known a focal-plane shutter equipped with a buffering member absorbing the impact caused by stopping of a shutter. For example, the buffering member is provided to abut the shutter at a stop position thereof. Such a focal-plane shutter is disclosed in Japanese Unexamined Patent Application Publication No. 2011-170226.
A drive pin of a drive lever is engaged with an engagement hole of a drive arm, and the drive arm drives in response to swinging of the drive lever. A swinging range of the drive lever is restricted by a predetermined restriction portion. Even after the swinging drive lever abuts the restriction portion and stops, the inertia force exerting on the drive arm pushes an edge of the engagement hole of the drive arm to the drive pin of the drive lever. Therefore, depending on a material of the drive arm, the edge of the engagement hole of the drive arm might be deformed.
Conceivably, the way to solve such a problem is to thick the shutter or to change material thereof to harder one.
Incidentally, in order to increase speed of the shutter driven by the drive lever, or in order to reduce a drive current of an electromagnetic actuator driving the drive lever, it is required to thin the shutter for weight reduction or to use a synthetic resin-made shutter in some cases.
When the shutter is thinned to prevent the deformation, the weight increases. This might not increase the drive speed of the shutter or this might increase the drive current.
Further, when the material of the arm is changed to a rigid one to prevent the deformation of the engagement hole of the arm, the weight of the arm increases depending on the material. This might not increase the speed or this might not decrease the drive current. Also, even when the speed can be increased or the drive current can be decreased, the manufacturing cost might increase.